No, but you can accomplish the same thing by buying a HiFi VCR (they go for well under $100 nowadays). Route the cable or antenna into the VCR, and use the audio output from the VCR. You use the VCR tuner to change channels, and your TV stays on channel 3 (or 4). I am assuming you use the video input on your TV for the DVD player. HTH
Where would you connect the RF modulator to? I think your most practical solution is doing what Rick Nolan recommends. Get a VCR with a tuner. Either that or get a newer TV .
I am obviously not familiar with every modulator on the market. However, every one I've seen has audio/video INPUTS and an RF OUTPUT. Typically these are used to connect newer components (DVD especially) to an older TV with only a antenna/cable input. So, without knowing more about your modulator, I'd have to say: no, won't work. BUT I could very well be wrong.....